At least 20 traffic accidents on expressways were reported yesterday morning, including one involving nine vehicles, with heavy rain possibly having a hand in these.

The nine-vehicle accident on the Central Expressway (CTE) towards the city caused a jam that extended for kilometres.

The Singapore Civil Defence Force was alerted to the CTE accident at 9.30am, and sent two ambulances to the scene.

The pile-up involved six cars, a taxi, a lorry and a motorcycle, and happened on the CTE towards the Ayer Rajah Expressway (AYE), near the Cairnhill exit. The Straits Times understands that the accident took place across two lanes.

The motorcyclist and a passenger of the taxi were taken conscious to the Singapore General Hospital, said the police. Investigations are ongoing.

At around 10am, the traffic tailback on the CTE stretched several kilometres to the Ang Mo Kio Avenue 5 exit, said a tweet by the Land Transport Authority (LTA).

At least 20 accidents took place on expressways before 11am yesterday, according to commuter alerts on the LTA's Twitter account.

Between 7am and 11am, there were at least seven accidents on the Pan-Island Expressway, five on the AYE and two on the Tampines Expressway.

Mr Lee Tian Min, 61, was travelling from Braddell Road to Tanjong Pagar when he passed by the CTE accident site around 10.15am.

"I saw two rows of vehicles piled up against each other and they took up two lanes. Cars on the road were moving very slowly," he said.

Mr Lee, a crane operator who was driving his wife to work, said the journey took him half an hour instead of the usual 10 minutes.